It is becoming important that casting patterns and their associated tools be developed faster in free-form, at lower cost, having superior surface finish and/or requiring little or no remachining. Although there are technologies that are currently used for forming ceramic articles, each has significant disadvantages that fail to meet all of the objectives.
For ceramic prototypes, the prior art has relied on complex processes to form these objects. These methods include the pressing of ceramic powders with subsequent sintering and machining into a final shape. Ceramic objects of this type may include mold shells that are used in casting. Nevertheless, this process is also slow and expensive.
Another method is selective laser sintering. Selective laser sintering (SLS) is a powder-based layer additive manufacturing process generally meant for rapid prototyping. Laser beams, either continuous or pulse mode, are used as a heat source for scanning and joining powders in predetermined sizes and shapes of layers via a polymer binder. The geometry of the scanned layers corresponds to the various cross-sections of the computer-aided design (CAD) models. A drawback of SLS is that additional powder at the boundaries is often hardened and remains attached to the part, thereby requiring additional finishing steps to remove the unwanted material. Furthermore, an inert atmosphere is often required, increasing the cost of the equipment.
Other prior methods include direct or indirect sintering processes. In a direct metal-laser-sinter process, the process operates essentially in the same manner as SLS, except that no binder is required. In this method, the ceramic is directly sintered by the laser.
Another prior art system is a fused deposition modeling system. The fused deposition modeling (FDM) system was designed to create prototype parts using thermoplastic or wax filaments. With this system, the filament is fed through the nozzle where it is heated just above its solidification temperature. The heated filament is then deposited onto the previous layers where it solidifies, forming the part. The movement of the heated nozzle is controlled by a sliced CAD model. In the ceramic FDM process, the filament is produced from a mixture of ceramic powder and binder material. The ceramic-binder filament is used in the equipment in the same manner as the thermoplastic filament. After a green part is formed from the ceramic-binder filament, the binder is removed by conventional means and the resulting ceramic parts are sintered to high density. In this method, the binder has to be removed and the resulting ceramic parts are sintered to high density.
Yet another prior art method is 3-D printing. 3-D printing uses a drop on demand jetting technology that is similar to ink jet printing. In this method the devices deposit a binder onto a powder bed. As the binder solidifies, a layer of solid geometry is created. As in FDM, the binder has to be removed and the resulting ceramic parts are sintered to high density.
Still another method is laminated object manufacturing (LOM). The LOM system normally uses thin sheets of paper to build up a wood-like component. The system is adapted to work with engineered ceramic materials using tape-cast ceramic sheet materials suitable for lamination. During the LOM build process, a laser, controlled by the machine's software, cuts the part cross-section onto a ceramic tape. A new layer of material is laminated to the previous cut layer. The process is repeated until the part is finished.
Accordingly, what is needed is a method of ceramic core prototypes that is faster than prior art methods. Also what is needed is a method of forming ceramic core prototypes that provides greater flexibility in changing the design of the ceramic core after formation. Also what is needed is a method of forming ceramic core prototypes that may be used in the formation of many different ceramic core articles or ceramic articles in general.